I think that in some ways, exercising self-discipline is harder than ever before.
We're all encouraged to feel something should entertain us before it is worthwhile.
We become brainwashed with messages like:
"Don't do it unless you feel like it!"
"If it feels good, do it!"
"You have to have passion for it!"
Choosing to do something or not based on whether it feels comfortable/pleasurable or not is a disaster.
If I waited to 'feel like it' before exercising or working or making that tricky phone call or putting in the occasional all-nighter to meet a deadline, then I would be fat, poor, untrusted and unsuccessful.
"Don't have a wishbone where your backbone should be!"